Electronic device for generating or amplifying high frequency oscillations



Nov. 19, 1963 N. B. AGDUR 3,111,604

ELECTRONIC DEVICE FOR GENERATING OR AMPLIF'YING HIGH FREQUENCY OSCILLATIONS Filed, June 5, 1961 Fig. 7

. IIIIIIIIIIIIIIIIJ IIIIIIIIIIIIIIIIA I /v l/E'N roR M4 5 BERT/L 9G0 UR Br H United States Patent ELECTRONIC DEVICE FOR GENERATING 0R AMPLEYILNG HHGH FREQUENCY 036E LATIGNS Nils Bertil Agdur, Stockholm, Sweden, assignor to Telefonaktiebolaget L M Eriesson, Stockholm, Sweden, a corpbration of Sweden Filed June 5, 1961, Ser. No. 114,791 Clfims priority, applicatinn weden lune 13, 1969 9 Qiaims. (til. 315-39) The present invention relates to an electron device for amplification or generation of high frequency electrical oscillations. The purpose of the invention is to provide a novel and improved electronic device, in which earlier used metallic wave-guide structures are replaced by an electronic medium, whereby it is possible to avoid certain inherent mechanical difiiculties at the manufacturing, as certain dimensions will necessarily be smaller than the wavelength with which the device will operate. An arrangement according to the invention comprises an electron source for generation of an electron beam and a magnetic field source for generation of a static magnetic field along the path of the electron beam in the space where the electron beam passes, The arrangement is characterized thereby that the electron source, the magnetic field source and said room are so dimensioned and shaped that within an interjacent piece of the path of the electron beam in said space the following conditions are satisfied:

where w is the angular frequency of the high frequency electrical oscillations,

w is the plasma frequency of the electrons, which together with the electrons generated by the electron source, are in said room, and

w is the gyro-frequency of the electrons in said room,

so that the phase velocity at the high frequency electrical oscillations is approximately equal to the velocity of the electron beam, while on each side of said interjacent piece at least one of the magnitudes w and w has such a value different from the corresponding value of the interjacent piece that the phase velocity at the high fre quency electrical oscillations successively reaches at least the velocity of light in vacuum. The control of the phase velocity is efiected by the magnitude w The invention will be further described in connection with the drawing, where FIG. 1 quite schematically shows an arrangement according to the invention, FIG. 2 shows a graph of the field from a magnetic field source included in the arrangement according to FIG. 1, FIG. 3 shows a diagram over the amplification factor of the arrangement according to FIG. 1, FIG. 4 schematically shows a modification of the arrangement according to FIG. 1 and FIG. 5 shows a ferrite tube intended for possible use in a modified type of the arrangement according to FIG. 1.

In an oval evacuated metal tube 5 there is an electron source 1, which generates an electron beam 2 passing through the tube 5 to a collector 7. The tube 5 is divided by a flanged partition wall in two chambers, 4 and 6, in one of which (6) the electron source 1 is situated. The wall 8 is shaped with a relatively long tubular part in the direction of the electron beam, which part is so dimensioned that with a continuously vacuum pumping from the chamber 6 the pressure in this part will be substantially smaller than in chamber 4. A gas inlet, not shown, is connected to the chamber 4-. As an example of practical pressure values 10" or 1O mm. Hg in the chamber 6 and 10 mm. Hg in the chamber 4 may be mentioned.

The electron beam when passing through the chamber 4 generates a plasma due to the collision between the electrons and the existing gas molecules, which plasma is the medium, by means of which amplification or oscillating generation is obtained.

Two rectangular wave guides 9, 16 respectively are connected to the tube 5. When the arrangement operates as an amplifier, signals are fed to the wave guide 9, and amplified signals are obtained at the wave guide 10. When the arrangement operates as an oscillator, the oscillation is obtained from the wave guide 9.

A magnetic field source 3 is concentrically arranged about the tube 5, which magnetic field source consists of an inner coil 30 and three outer coils 31, 32 and 33, of which the coil 32 is placed between the coils 31 and 33. The magnetic field source is so dimensioned that its field is substantially constant along an intermediate length [1-1) of the path of the electron beam in the chamber 4 and decreases successively on each side, ca, bd, respectively, of this length, see FIG. 2.

If amplified oscillations of the angular frequency w are to be generated, these are, as earlier mentioned, fed to the wave guide 9. The electron source 1, the magnetic field source 3 and the chamber 4 are then so dimensioned that the following conditions are satisfied within the length a-b of the chamber 4:

where w is the angular frequency of the electrons in the chamber 4 and w is the gyro-frequency of these electrons. The phase velocity by the electrical oscillations should be approximately equal to the velocity of the electron beam within said length ab. At each side of said length 11-15 at least one of the magnitudes w and w should have a value different from the corresponding value within the length a-b that the phase velocity of the electrical oscillations will successively reach at least the velocity of light in vacuum. In this way amplified oscillations can be obtained at wave guide 10. Practical experiments have shown that the current value of the electron beam must be below a certain critical value i as otherwise the arrangement operates as an oscillator. This is intimated in FIG. 3 where the curve part 1 indicates the amplification case and the curve part 0 the oscillation case.

If high frequency electrical oscillations of the angular frequency w are to be generated the conditions mentioned in the foregoing concerning the magnetic field source and the chamber 4 must be satisfied and the current value of the electron beam must exceed said critical value f if a relatively tight plasma is wanted or if it is wanted to be able to use a relatively low gas pressure in the tube, it is suitable to put in a resonator to the right of the wave guide 10 and optionally also to the left of the wave guide 9, which resonator is excited so that it generates an electrical field along the electron beam and thereby reduces the losses of plasma-electrons in axial direction. This case is shown in FIG. 4 where 41 and 42 indicate the aforementioned resonators.

In the arrangement now described the electron beam itself has generated the plasma required for the function of the arrangement. In certain cases, however, it may be desirable not to use the electron beam to generate a plasma, and in such cases a separate discharging arrangement can be provided in the chamber 4 and a gas of suitable kind and pressure, which gas then is changed to a plasma due to the action of the separate discharging arrangement. A mercury discharge or a discharge in an inert gas may for instance be used.

The magnitudes w and w mentioned in the foregoing can be defined in the following way:

where e is the charge of the electron,

m is the mass of the electron see is the number of electrons/m.

60 is the dielectric constant for vacuum, and

B0 is the magnetic field power from the source 3.

From this it appears that it is not necessary with a plasma as transmission medium, but it is possible to provide ferrite tube in the tube 4, see FIG. 5, in the center of which the electron beam may pass. In this case w corresponds to the magnetic dipole moment/unit of space of the ferrite tube. In this case the ferrite tube should be covered with a thin metal film, which allows passage of micro Waves and at the same time can lead away electron accumulations if any.

From the now mentioned details it is clear that with a suitable medium (plasma or ferrite), which is given a suitable electron density (use of plasma) or a magnetic dipole density (use of ferrite), and an outer static magnetic field it is possible to obtain an electron tube arrangement with the following qualities: An electromagnetic wave can be amplified by means of an electron beam, which passes through the medium. The energy velocity of the electr c-magnetic wave may obtain a direction opposite the direction of the phase velocity of the wave. By suitably varying the static magnetic field and/ or the density of the medium along the beam, the amplified wave can radiate from the electron beam. As it is evident many other forms of embodiment may be provided without departing from the scope of invention.

I claim:

1. In an electronic device for generating high frequency oscillations and amplifying high frequency oscillations, an envelope containing a gas maintained at a predetermined gas pressure, an electron source for directing an electron beam into said envelope, and a magnetic field source for generating a static magnetic field along the path of the beam within said envelope, said electron source and said magnetic field source being so correlated that in a length of the beam intermediate the source of the beam and the end of the beam in the envelope the following conditions prevail:

2 2 and w w +w where w is the angular frequency of the high oscillations, ar is the angular frequency of the electrons in said envelope, and w is the gyro frequency of the electrons in said envelo-pe,

whereby the phase velocity of the high frequency oscillations within said intermediate length of the beam is approximately equal to the velocity of the electron beam and at least one of the magnitudes w and w has on both sides of said intermediate length a value different from the corresponding value within the intermediate length of the beam and decreases gradually with increasing distances from said length to values at which the phase velocity of the high frequency oscillations on both sides of said intermediate length gradually reaches at least the velocity of light in vacuum.

2. An electronic device according to claim 1, wherein a first wave guide is connected to said envelope between said electron source and said intermediate length of the beam and a second wave guide is connected to said envelope between said length and the end of the beam in the envelope, high frequency oscillations being obtainable at said first wave guide and signals to be amplified being fed to the envelope at said first wave guide and taken out at said second wave guide.

3. An electronic device according to claim 1, wherein said magnetic field source is arranged and disposed to generate a substantially constant magnetic field along said intermediate length of the beam and a gradually decreasing magnetic field along the beam adjacent both ends of said length.

4. An electronic device according to claim 1, wherein said envelope is filled with a gas at a pressure such that the gas becomes a plasma zone when passed by the electron beam.

5. An electronic device according to claim 1, wherein said envelope includes a discharge means and is filled with a gas at a pressure such that the gas is converted to a plasma by the action of said discharge means.

6. An electronic device according to claim 1, wherein said envelope is filled with a gas at a pressure such that it becomes a plasma zone when passed by the electron beam, and wherein a resonator generates an electric field lengthwise of the beam to compensate for losses of plasma electrons.

7. An electronic device according to claim 1, wherein a tube made of ferrite is interposed in the path of the beam, the beam passing through said tube.

8. In an electronic device for generating high frequency oscillations and amplifying high frequency oscillations, a gasilled, generally tubular envelope, an apertured transverse partition wall dividing said envelope into two chambers, said chambers being maintained at different gas pressures, an electron source in the chamber at the higher vacuum and an electron collector in the other chamber at the end thereof distant from said partition wall, said electron source directing a beam of electrons through said apertured partition wall upon said collector, and a magnetic field source for generating a static magnetic field along the path of the electron beam within said other chamber, said electron source and said magnetic field source being so correlated that in a predetermined length of the beam intermediate said partition wall and said collector the following conditions prevail:

and

where w is the angular frequency of the high oscillations, w is the angular frequency of t.e electrons in said envelope, and i w is the gyro frequency of the electrons in said envelope,

whereby the phase velocity of the high frequency oscillations within said intermediate length of the beam is approximately equal to the velocity of the electron beam and at least one of the magnitudes w and w has on both sides of said intermediate length a value difierent from 3,111,eoe

5 the corresponding value Within the intermediate length of the beam and decreases gradually with increasing distances from said length to values at which the phase velocity of the high frequency oscillations on both sides of said intermediate length gradually reaches at least the velocity of light in vacuum.

9. An electronic device according to claim 8, wherein said magnetic field source comprises an inner coil coaxial With said envelope and extending along said intermediate beam length, protruding at both ends therefrom,

and three outer coils axially aligned with each other and coaxial with the envelope, the intermediate one of said outer coils being substantially coextensive with the inner coil and the two outer ones of the outer coils being disposed adjacent the electron source and the collector.

References {Jited in the file of this patent UNITED STATES PATENTS Norton June 3, 1958 Bryant Aug. 19, 1958 

1. IN AN ELECTRONIC DEVICE FOR GENERATING HIGH FREQUENCY OSCILLATIONS AND AMPLIFYING HIGH FREQUENCY OSCILLATIONS, AN ENVELOPE CONTAINING A GAS MAINTAINED AT A PREDETERMINED GAS PRESSURE, AN ELECTRON SOURCE FOR DIRECTING AN ELECTRON BEAM INTO SAID ENVELOPE, AND A MAGNETIC FIELD SOURCE FOR GENERATING A STATIC MAGNETIC FIELD ALONG THE PATH OF THE BEAM WITHIN SAID ENVELOPE, SAID ELECTRON SOURCE AND SAID MAGNETIC FIELD SOURCE BEING SO CORRELATED THAT IN A LENGTH OF THE BEAM INTERMEDIATE THE SOURCE OF THE BEAM AND THE END OF THE BEAM IN THE ENVELOPE THE FOLLOWING CONDITIONS PREVAIL: 